[libc] Enable a few stdlib and time functions on aarch64.

libc/config/linux/aarch64/entrypoints.txt

@@ -245,6 +245,12 @@ if(LLVM_LIBC_FULL_BUILD)
     libc.src.stdio.stderr
     libc.src.stdio.stdout
 
+    # stdlib.h entrypoints
+    libc.src.stdlib._Exit
+    libc.src.stdlib.atexit
+    libc.src.stdlib.exit
+    libc.src.stdlib.getenv
+
     # threads.h entrypoints
     libc.src.threads.call_once
     libc.src.threads.cnd_broadcast
@@ -290,6 +296,13 @@ if(LLVM_LIBC_FULL_BUILD)
     libc.src.pthread.pthread_mutexattr_setpshared
     libc.src.pthread.pthread_mutexattr_setrobust
     libc.src.pthread.pthread_mutexattr_settype
+
+    # time.h entrypoints
+    libc.src.time.asctime
+    libc.src.time.asctime_r
+    libc.src.time.gmtime
+    libc.src.time.gmtime_r
+    libc.src.time.mktime
   )
 endif()
 

libc/config/linux/x86_64/entrypoints.txt

@@ -259,7 +259,6 @@ if(LLVM_LIBC_FULL_BUILD)
 
     # stdlib.h entrypoints
     libc.src.stdlib._Exit
-    # libc.src.stdlib.abort
     libc.src.stdlib.atexit
     libc.src.stdlib.exit
     libc.src.stdlib.getenv

libc/loader/linux/aarch64/start.cpp

@@ -118,6 +118,7 @@ extern "C" void _start() {
   // value. We step over it (the "+ 1" below) to get to the env values.
   uint64_t *env_ptr = app.args->argv + app.args->argc + 1;
   uint64_t *env_end_marker = env_ptr;
+  app.envPtr = env_ptr;
   while (*env_end_marker)
     ++env_end_marker;